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A coastal flood protection system consisting of a primary dike as the key element safeguards the Lower Saxony mainland coast against flooding. The flood-prone low-lying coastal marshlands show an elevation partly below mean high tide level and would therefore be flooded twice a day without any protection system. Storm surges and sea level rise can lead to water levels several metres above mean high tide, hence modern dikes are designed to withstand these loads. In front of approx. 70% of the coastal dikes, a foreland as an ecosystem-based element of the coastal protection system exists, providing additional safety. Using the example of the area of the Dike Board Esens-Harlingerland, the effect of the foreland in case of a failure of the coastal protection system due to a dike breach, was evaluated. Water depth, flood propagation and the estimated damage associated with the flooding were examined based on scenarios.
Typical sections of the existing coastal defence system were jointly identified with the Dike Board. This was followed by numerical simulations and damage assessments. A workshop with all key stakeholders was organised and resulted in a collective agreement on importance of the ecosystem-based element foreland and its increasing value under climate change and sea level rise conditions. It also provided a better understanding of the whole coastal protection system in case of a failure, identification of adaptive pathways to maintain the foreland and future collaboration with stakeholders that will also focus on additional aspects, such as disaster prevention and management.
Two pillars played a prominent role in the case study for Lower Saxony. The first one is the whole-system approach, which made it possible to map the relationship between the characteristics of the foreland and the expected damage in the event of a failure. The source-pathway-receptor concept was chosen to analyse this relationship. In this case, this approach consists of the elements “North Sea (source) – foreland and dike (pathway) – drainage system of the hinterland (pathway) and inhabited areas (receptor).” Using the whole-system approach, the process offers an opportunity to communicate and discuss the interdependency and impacts of climate change in a broader perspective and to overcome siloes.
The second prominent Cloud-2-Coast pillar is a continuous dialogue. The case facilitated the existing cooperation and involved additional stakeholders to cover all aspects addressed in the whole-system approach. It was started as a small and project-based group and continue as part of the project in mutual learning to consider climate change adaptation of the Lower Saxony coastal protection system.
The implementation of the coastal protection measures that have been carried out so far and are currently planned will continue to be a reasonable option for sustainable protection of the coastal lowlands in the coming decades against flooding. This is important especially within the framework of the Lower Saxony climate change adaptation strategy and the measures described therein, such as the climate dike and forelands as significant elements of the coastal flood protection system. By applying the Cloud-2-Coast approach, these measures could probably be implemented more easily, as adaptation pathways and the involvement of relevant stakeholder groups will facilitate the planning and approval processes.